1. Field of the Invention
The present invention relates to an antireflective structure which is excellent in electromagnetic wave antireflectivity as well as scratchproof.
The present invention also relates to an antireflective molded body which includes the above antireflective structure and is preferably used as a non-reflective panel for bodies, various meters, displays and the like of vehicles (automobiles), ships, aircrafts and the like.
2. Description of the Related Art
In such fields as aircrafts, automobiles, ships and the like, antireflection of electromagnetic wave is necessary for such applications as: i) stealth technology not viewed on radar, ii) an IR measurement camera, a meter cover, a liquid crystal display which are used for measuring vehicle-to-vehicle distance, and the like.
For example, a driver's seat of an automobile has a meter front cover which is embedded in a front face of a display where various meters such as speedometer, fuel meter and the like are received in combination. In this case, however, the scenery outside the vehicle is imaged in through a front window or a side window to the meter front cover, as the case may be, making it difficult to view the various meters of the display. For preventing the above invisibility, a meter hood is disposed above the various meters for blocking an external light from entering the meter display.
A structure including a plurality of thin films having different refractive indexes are conventionally known as a multilayer antireflective film which is used for preventing reflection of the light as stated above.
Japanese Patent Application Laid-Open No. 2002-267815 (=JP2002267815) discloses an antireflective structure using a fine structure, where the antireflective structure is more excellent in lowering reflectivity than the above multilayer antireflective film.
JP2002267815 discloses an antireflective structure where a myriad of fine iregularities (fine protrusions and dents) made of transparent material are formed on a surface of a transparent molded body at pitches each less than or equal to a wavelength of light such that the refractive index of the light varies in the thickness direction.
When a myriad of fine irregularities (fine protrusions and dents) each of which is corrugated or triangular in cross section are formed on the surface, occupancy (ratio of presence) of the transparent material on the outermost surface of the irregularities is limitlessly closer to 0%, which is a state substantially causing a refractive index of air.
Meanwhile, at the base face of the irregularities, occupancy of the air is limitlessly closer to 0%, which is a state substantially causing a refractive index of the transparent material.
Furthermore, an intermediary part of the irregularities has an refractive index according to the cross section occupied by the transparent material.
As such, the refractive index of light continuously varies between the refractive index of air and the refractive index of transparent material in the thickness direction of the antireflective structure.
As a result, according to a principle like that of the multilayer antireflective film having a plurality of thin films with different refractive indexes which vary stepwise, the antireflective structure of JP2002267815 is more excellent than the multilayer antireflective film.
However, JP2002267815 may cause scratches to the surface of the antireflective structure, as the case may be, deteriorating the antireflectivity.